Download ch-7 [Basic Chemistry]

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•
Matter is everything in the universe that has a mass
(weight) and volume
Examples: air, water, bacterium, and human
• Atom is the smallest piece of matter.
introduced by Democritus (Greek philosopher)
in 450 B.C
It is Greek word meaning indivisible
•
The atom concept was restored by the English
chemist John Dalton in 1803
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States of matter: matter can be solid, liquid, or gas
Solid
• Has Fixed volume and shape
• Does not take the shape of container
Liquid
• Has fixed volume and take the shape of container
• Fills the container according to hits volume
Gas
• Has no fixed shape and no fixed volume
• It takes the shape of container whatever volume it
has
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Matter is anything that has mass and takes up
space.
• How It Looks (Shiny ,Dull, Color, etc.)
• How It Feels (Hard, Soft, Rough , Smooth,
etc.)
• How It Smells (Sweet, Sharp, Terrible, No
Smell, etc.)
• How It Sounds (Loud, Soft, Echo, No Sound,
etc.)
• What It Does (Bounce, Stretch, Tear, Break,
Magnetism etc.)

A solid is matter that has that has definite size
and shape.

Particles of solids are tightly packed, vibrating
about a fixed position.

Solids have a definite shape and a definite
volume.

A liquid takes the shape of any container.

Particles of liquids are tightly packed, but are
far enough apart to slide over one another.

Liquids have an indefinite shape and a definite
volume.

Gas is matter that has no definite shape. Gases
take the shape of whatever container they are in.

Particles of gases are very far apart and move
freely.

Gases have an indefinite shape and an
indefinite volume.
Description of
Phase Change
Solid to
liquid
Liquid to
solid
Term for Phase
Change
Heat Movement During
Phase Change
Melting
Heat goes into the
solid as it melts.
Freezing
Heat leaves the liquid
as it freezes.
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mixture is a group of two or more elements or compounds combined by
physical (not chemical) means
• Examples: Milk, blood, sand, pizza, and wood
Homogeneous mixture is one that has constant matter in all the sample
- example: a well stirred sample of sugar and tea
Heterogeneous mixture is one that has not constant matter in the all the
sample
- example: Milk, blood are good examples
Mixtures can be separated by physical means only like filtration
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1. The electron discovered in 1897 by the J.J. Thompson using
cathode ray vacuum tube
• electron has a charge of  1.6 10 19 Coulomb
•
electron has a mass 9.111031 kg
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2. The nucleus (proton) discovered by Ernest Rutherford in 1907
Rutherford conclusion
•
•
•
The atom is mostly empty space, has a central part called a nucleus surrounded by
electrons
The nucleus is small, dense concentration of mass and contains a positive charge
Any positive charge projected into the nucleus would be deflected due to a
repulsive force
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• In 1919, Rutherford concluded that the hydrogen nucleus is indeed
a positively charged particle he called the proton that is present in
all nuclei.
Scientist realized that the proton is about 2000 times heaver that
the electron and the magnitude of its charge is the same as that of
the electron, but with a positive sign, +1.6 10-19 C.
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3. The neutron discovered by James Chadwick in 1932
Chadwick conclusion
• The neutron is uncharged particle
• Its mass is approximately equal to that of the proton
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A model is a picture of atom. Two models
• Thomson’s model 1889: The plum pudding model
- atom is a sphere with positive charge like ”pudding”
electrons distributed equally like a “plum”
- atom mass distributed all over the atom
•
Rutherford’s model 1911: The planetary model
- the nucleus (like the sun) at the centre of the atom surrounded by a cloud of
orbiting electrons (like the planets).
- Most the atomic mass is concentrated in its nucleus (why?).
- The Coulomb force is responsible of keeping
the electrons orbiting the nucleus.
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Max Plank in 1900: the energy emitted by hot objects (solid, liquid, and gas) is
emitted in a discrete units or bundles he called quanta plural of a quantum and is
related to the frequency f of the emitted quantum hf by some whole number
multiple of or
E  hf
Plank’s constant
h  6.626  10 34 J . sec
Albert Einstein (1905) applied Plank’s quantum concept to light.
- light consists of discrete units or bundles of energy called photons
- The energy of a photon is directly proportional to its frequency.
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Why does an atom emits (gives off) light of different colors
(spectrum)?
• Light from hydrogen gas in a bulb
- Separated 4 lines of colors.
- Only hydrogen has these colors
- Each color represents a frequency
- Other gases have different set of colors
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The electron orbits the proton in allowed circular orbits identified by numbers:
with n=1 is the orbit with the lowest energy (ground state).
The orbits are separated from one another by empty space where the electrons
cannot exist
The electron in an allowed orbit does not emit light as long as it remains in that
orbit
Electrons can move from one orbit to the next by gaining or losing energy
when electron gains energy. it jumps from an allowed lower to an allowed higher
orbit (2-3). Once in a high energy orbit, the electron immediately jumps back to its
initial orbit and emits light (photon)
The photon represents a certain frequency f (color) , and carries energy given by
E  E final  Einitial  hf
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
The total mass of an atom is called its Atomic Mass.

It is the sum of the masses of all the atom’s components
(electron, proton and neutrons).

The number of protons in the nucleus of an
atom determines an element's atomic number.

In other words, each element has a unique
number that identifies how many protons are
in one atom of that element. 8.
For example,
 The hydrogen atom contains one proton
and have an atomic number of 1.
 The carbon atom contains six protons and
have an atomic number of 6.
 The Oxygen atoms contain eight protons
and have an atomic number of 8.
• The mass number (A), also called atomic mass number
or nucleon number, is the total number of protons and
neutrons (together known as nucleons) in an atomic
nucleus.
• All atoms have a mass number which is derived as follows.
Number of neutrons
Number of Protons
An atom (element) is identified by a symbol (letter) with its Z and Anumbers written at the lower and upper left of the symbol. Example, carbon
and silver are identified as
A
Z
X:
12
6
C,
108
47
Ag
Example
For each of the following atoms, determine (a) A, (b) Z, and (c) N numbers.
Find also the number of electrons. Assume the atoms are at normal
conditions:
59
27
Co,
96
42
Mo, and
133
55
Cs
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 One of two or more atoms with the same atomic number but
with different numbers of neutrons.
Or
 One of two or more atoms having the same atomic number but
different mass numbers.
Examples of Isotopes:
 A tabular arrangement of the elements according to
their atomic numbers so that elements with similar
properties are in the same column.

Two other important ways in which the
elements are organized in the periodic table are by
horizontal rows and vertical column.

Each horizontal row is called a Period and each
vertical column is called a Group (or some times a
family).

There are 7 periods and 18 groups.